Process of refining petroleum



Aug. 14, 1934. TUMSTRA 1,969,956

PROCESS 0F REFINING PETROLEUM Filed July 9, 1927 fLf l '2f Patented Aug. 14, 1934 UNITED STATES PATENT OFFCE to Shell Petroleum of Virginia Corporation, a corporation Application July 9, 1927, Serial No; 204,499

5 Claims.

This invention relates to the art of refining petroleum oils, and consists in the novel procedure hereinafter disclosed.

It is recognized in the art that, when light oils, such as motor fuels, are produced from a charging stock of heavy oils by the cracking process, the motor fuel fractionated from the cracked oil contains many undesired unsaturated constituents, which give rise to an objectionable color and to the formation of gums and other solid bodies in the final product. It is generally understood that, when the temperature of the charging stock is raised to cracking temperatures under pressure sufficient to cause the decomposition or disruption of the molecular structure, a chemical change occurs which forms the lighter oilfractions, and also other light fractions which tend to create gums or other bodies that are carried over with the motor fuel or gasoline fractions, which give a detrimental color to the iinished product.

It has been discovered that, by subjecting the synthetic crude resulting from the cracking operation to a lower temperature for a suitable length of time, at which the velocity of cracking is greatly reduced, yet the temperature sumciently high to cause polymeriaztion of those unstable components of the lighter or gasoline fractions which tend to create gums and other colored bodies, a final product of satisfactory color, which is also substantially free from unsaturated constituents that tend to form gums or other similar bodies, is produced.

It is the object of the present invention, therefore, to provide a process for the continuous treatment of selected charging stock, such as gas oil, kerosene, or other petroleum oils, whereby the heavy oil is first subjected to a cracking operation, then the temperature reduced to a point where the velocity of cracking is greatly reduced, and holding the synthetic crude for a lperiod of time and in a relatively large body at a temperature that is suiiiciently high to polymerize or stabilize the gasoline fractions; and then fractionate the gasoline fractions from the oil.

The complete advantages of the process will be apparent to those skilled in the art from the following detailed description thereof, taken in connection with the accompanying drawing, in which a suitable form of apparatus for practicing the process is diagrammatically disclosed.

In the practice of the invention with the apparatus disclosed in the drawing, which will be understood to be merely illustrative, the charging stock is pumped from the charging tanks `1 through a line 2 by means of a charging-pump 3.

Where thefinal product is gasoline or motor fuel, it will be understood that the ordinary starting material will be the heavier oils, such as gas oil, kerosene or other heavy petroleum oils. The line 2 connects with coils 4 in the upper part of a fractionator 5the purpose being to utilize the cooling effect of the charging stock passing through said coils at the top of the fractionator, as will more fully appear hereinafter. f

From the coils 4, a line 6 leads to an accumulator 7 from which the stock is advanced through a line 8 to a tube system 9 of a still 10, there being interposed in the vline 8 a pair of pumps 11 and 12 arranged in tandem to transfer the stock from the accumulator to the tube system of the still under pressure. In ordinary practice the pressure is raised from atmospheric to 300 to 800 pounds gage. Y Thev stream is heated in the still by a furnace 13 to cracking temperature, ordinarily from 750" to 900 Fahrenheit, and the cracking oi the material is set up in the tube system of the still and continues in the reaction chamber 14 with which the tube system of the still is connected by a line 15. The cracking operation proceeds in the reaction chamber until the point of maximum economic cracking of the material has been accomplished. It will be understood that the time Vthat the material is subjected to treatment in the tube system and inthe reaction chamber is controlled by the throughput of the material from the accumulator.

After the cracking of the oil has proceeded to the predetermined point, it is withdrawn from the reaction chamber through a line 16 and passed through the coils 17 of a cooler 18, where the temperature is dropped from cracking temperature to a temperature of about 600 to 700 Fahrenheit, at which temperature it is introduced through a line lQ-into a polymerizer chamber 20, where it is held at this temperature for a predetermined time, dependent upon the material subjected to treatment.

The reaction-chamber comprises an open shell whichV is vpreferably heat-insulated so that the temperature is held in the reaction chamber at substantially the still temperature, in order that the cracking, with full effect, may proceed. The dropping of the temperature in the cooler may be accomplished by air or water cooling, or by other means. y

The polymerizer chamber comprises also an open shell, preferably heat-insulated.

The relative time between the cracking reaction and the polymerizing reaction can be conico trolled by the relative throughput from the reaction chamber to the polymerizer chamber, either by coordinating the dimensions of each of the chambers, or by an arrangement of manifold outlets from the reaction chamber. It will also be understood that the pressure in the polymerizer chamber remains the same as the still pressure.

In ordinary practice, the treatment of the synthetic crude from the reaction chamber in the polymerizer chamber at a temperature of from 600 to 700 Fahrenheit for a period of thirty minutes to one hour will be suiiicient to complete the polymerization or stabilization of the gasoline fractions, so that the synthetic crude, after the polymerizing treatment, contains gasoline fractions having a color test of approximately 25 Saybolt, or better.

For a matter of comparison, the gasoline fractions of the synthetic crude direct from the reaction chamber produce gasoline fractions having a color test of approximately 0 Saybolt. It is thus seen that the effect of subjecting the synthetic crude to the temperature below normal cracking temperature and at which the velocity of cracking is greatly reduced, yet of a degree sufficient to cause the stabilization of theV unsaturated molecules produces a product responding to a satisfactory color test.

The remaining steps of the procedure in relation to the treatment of the material after leaving the polymerizer chamber follow any approved fractionation procedure. As illustrated, the material is withdrawn from the polymerizer chamber through a line 21 in which there is a pressure reducing valve 22 for reducing the pressure to one suitable for the fractionation operation. The line 21 enters into the lower part of the fractionator 5, which preferably comprises a rectifying column wherein the lighter vapors are evaporated from the liquid. The coils 4 in the top of the fractionator 5 act as a cooler or dephlegmator to set up a reflux to wash out the heavier fractions which accumulate in the bottom of the fractionator, and are withdrawn through a line 23 to a steaming column 24 into the bottom portion of which there is connected a steam line 25 for injecting live steam through the column of liquid in the steaming column. The vapors from the upper part of the fractionator are Withdrawn through a line 26, through which they pass to a coil 27 of a condenser 28, and thence to a gas separator 29. It will be understood that the overhead product from the fractionator that leaves the fractionator through the line 26 contains the desired end point liquid when condensed, and, in ordinary practice, would comprise the gasoline component of the synthetic crude entering the fractionator.

Therefore, the uncondensed vaporsin the gas separator 29 are withdrawn overhead from the gas separator through a line 30 and returned to the recovery system, and the condensate from the gas separator is Withdrawn through a line 31 through a pressure-reducing valve 32, and is discharged to the gasoline run-down tank 33.

'Ihe upper part of the steaming column has connection lines 34 and 35 with the rectifying column intermediate of its height. The purpose of the connection 34 is to lead the fractions which are evaporated in the steaming column out of the liquid by means of open steam, back into the fractionating column 5. Part of the reflux formed by the cooling coils 4 in the fractionator 5 is led into the steaming column 24, through the line 35 to scrub the vapors in this column. There is also a connection from a point intermediate the height of the steaming column with the accumulator, said connection comprising the line 36 by which the refiux liquid, after scrubbing the vapors in the steaming column, is returned to the accumulator, where it is mixed with the incoming charging stock and is rerun through the cracking operation therewith.

The residue from the steaming column is withdrawn through a line 37, which passes through a cooler 38 to a residue run-down tank 39, through a line 40.

As above suggested, the fractionating equipment described is not essential to the invention, but any known form of apparatus for fractionating the synthetic crude after it has been treated in the polymerizer chamber may be used.

An important feature of the present invention is that the polymerization of the synthetic crude progresses to a high degree before it is subjected 'to the fractionating treatment and thereby attains a stabilization of the color-inducing and gum-forming constituents that impart to the final product an unsatisfactory color and an unstable characteristic as to color.

It is to be understood that the process is not limited to any particular form of equipment but that it is limited only by the appended claims.

What I claim and desire to secure by Letters Patent is:-

1. The process of treating hydrocarbon oils by subjecting the oil to a temperature and pressure condition to crack the oil to cause conversion of heavier fractions to lighter fractions whereby unsaturate gum forming constituents are produced, then cooling the oil to a temperature below a cracking temperature to arrest substantial conversion of heavier fractions to lighter fractions, then holding the body of oil in the reduced temperature zone at a temperature sufciently high and for a sufcient length of time to cause a stabilization of a substantial portion of the gumforming constituents in the oil by converting unstable gum-forming bodies to substantially stable heavier bodies.

2. The improvement in the process of treating hydrocarbon oils that have been subjected to temperature and pressure conditions to crack the oil to cause a conversion of heavier fractions to lighter fractions, consisting of cooling the cracked products to a temperature below that at which any substantial cracking reaction occurs and above 600 F., holding the oil at this temperature and at substantially the cracking pressure and for a period of time of approximately thirty minutes or more, so that the unstable bodiesproduced from the cracking operation yielding objectionable color and gum-forming constituents in the desired product are converted to heavy bodies and are removed in a subsequent fractionation operation from the final light oil product.

3. Ihe improvement in the process of treating hydrocarbon oils that have been subjected to temperature and pressure conditions to crack the oil to cause a conversion of heavier fractions to lighter fractions, consisting of cooling the cracked products to a temperature between 600 F. and 700 F., holding the oil at this temperature and at substantially the cracking pressure and for a period of approximately 30 minutes or more, so that the unstable bodies produced from the gumforming constituents in the desired product are converted to heavy bodies and are removed in a subsequent fractionation operation from the final light oil product.

4v. The improvement in the process of treating hydrocarbon oils that have been subjected to temperature and pressure conditions to crack the oil to cause a conversion of heavier fractions to lighter fractions, consisting of cooling the cracked products to a temperature below that at Which any substantial cracking reaction occurs and above 600 F., holding the oil at this temperature and at substantially the cracking pressure for a period of time between 30 and 60 minutes, so that the unstable bodies produced from the cracking operation yielding objectionable color and gum-forming constituents in the desired product are converted to heavy bodies and are removed in a subsequent fractionation operation from the nal light oil product.

5. The improvement in the process of treating hydrocarbon oils that have been subjected to temperature and pressure conditions to crack the oil to cause a conversion of heavier fractions to lighter fractions, consisting of cooling the cracked products to a temperature between 600 F. and '700 F., holding the oil at this temperature and at substantially the cracking pressure for a period of time between 30 and 50 minutes, so that the unstable bodies produced from the cracking operation yielding objectionable color and gumforming constituents in the desired product are converted to heavy bodies and are removed in a subsequent fractionation operation from the nal light oil product.

SIJBREN TIJMSTRA. 

